In diesel engines, to meet regulatory standards for reduced emission leveled, engine and vehicle manufactures use selective catalytic reduction (“SCR”) systems which inject a fluid, diesel exhaust fluid (“DEF”), into the exhaust. The DEF is typically stored in a reservoir and introduced into the exhaust on demand from an engine control unit. DEF is however subject to freezing if exposed to too cold of temperatures. As such, to prevent the DEF from freezing, engine coolant is diverted to a heating element in the reservoir to keep the DEF from freezing or to thaw the DEF if it is already frozen. A valve such as a poppet, diaphragm, or spool valve, typically electronically controlled, have been used as a control valve to control the flow of the coolant from the main coolant system to the heating element in the reservoir containing the DEF.
The electronically controlled poppet, diaphragm, and spool valves while operable do not perform as well as desired. These types of valve are susceptible to contamination and do not perform well when a low pressure drop is required.
Within automated or “commanded” valves, the gate is typically actuated by a solenoid and opened or closed in response to an electrical current applied to the solenoid coil. These solenoid-powered gate valves also tend to include a coil spring, diaphragm, or other biasing element which biases the gate towards an unpowered, ‘normally open’ or ‘normally closed’ position. Since the biasing force must overcome frictional forces resisting movement of the gate in order to return it to its normal position, and since the solenoid mechanism must overcome both these same fictional forces and any biasing force in order to move the gate to an actively-powered position, frictional forces tend to dictate much of the required solenoid operating force.
A good seal, between the inlet and outlets when the gate is closed, typically requires some degree of interference between the gate and the walls of the conduit. Increasing the design's interference to obtain a reliable, high quality seal (especially when accounting for component variation within reasonable tolerances) tends to increase both the frictional forces resisting movement of the gate and the required solenoid operating force. However, if seal reliability and quality could be maintained with lower frictional resistance, reductions in solenoid operating force would beneficially allow for a reduction in the size, weight, and heat-dissipation requirement of the solenoid mechanism, and thus for a reduction in the size, weight, and power demand of the gate valve as a whole. Such an improved gate valve is needed.